1. FIELD OF THE INVENTION
This invention relates to the field of fuels, and in particular, methanol fuels for use in internal combustion engines and turbine engines.
2. BACKGROUND ART
Modern internal combustion engines are high performance systems requiring maximum efficiency, reliability and safety. Materials engineering and mechanical improvements contribute to engine performance, but all engines are dependent in large part on fuel efficiency for performance. Therefore, various high performance fuels have been developed to maximize engine performance. The particular fuel chosen depends on the particular performance requirements of the engine under consideration, economic considerations, and current geopolitical realities.
Alcohol based fuels are popular fuel sources for internal combustion engines. Alcohol based fuels promote energy conservation and environmental protection because they can be produced from self renewing energy sources and because the burning of such alcohol based fuels creates less pollution than results from the burning of hydrocarbon fuels. High performance alcohol based fuels are often the fuel of choice in high end applications, such as in aircraft engines and racing engines.
One such high performance alcohol based fuel is methanol (methyl alcohol, CH30H), well known for clean (complete) combustion. In internal combustion engines, the more completely a fuel burns, the higher the fuel efficiency and ultimately engine efficiency. Thus, methanol is a very efficient fuel. However, there are several disadvantages associated with methanol.
One disadvantage with methanol is the fact that it is colorless in its liquid state. Since a variety of fuels are typically required and available for internal combustion engines, especially in aviation applications, it is necessary to color the fuels to distinguish one from the other. Therefore, it is desireable to have a dye for coloring methanol which does not compromise the performance characteristics of the fuel.
Another disadvantage of methanol as an engine fuel is a colorless flame. Hydrocarbon fuels typically have highly visible flames. However, a methanol flame is almost invisible, resulting in potential hazards. Therefore, it is desireable to provide an additive to methanol which will result in colored flame. In the past, flame colorants utilized with methanol have been solids, such as carbon, certain metal oxides or gasoline or other hydrocarbons, typically in the range of 15 to 50% composition. These additives often produce an emission that interferes with the clean burning of methanol. Therefore, it is desired to produce a flame colorant that does not interfer with the performance characteristics of methanol.
In the past, methanol fuel has been of high purity. There are certain combustion problems associated with the burning of high purity methanol. For example, thermal runaway can occur, where one cylinder overheats and the engine must be shut down. In formulating methanol fuel with added water, increased corrosion to exposed metals may result. Therefore, it is desireable to prevent such corrosion.
Another disadvantage of methanol fuel is a lack of good lubricating characteristics. This lack of lubricity can often cause pump seizures, erosion of ancillary equipment and degrading of moving metal surfaces in close contact. One prior art additive to improve lubricity is castor oil. However, castor oil requires high concentrations to be effective does not have a long life in methanol solution and may cause coatings to build up on engine parts. Further, such additives adversely affect combustion properties of the fuel.
Comparisons between lubricating additives have been difficult to quantify using prior art lubricity tests. In the prior art, fuel containing a lubricating agent is used to coat the surface of a metal piece which is brought into sliding contact with a second metal piece. The metal surface is observed until "pitting" occurs. For fuel such as methanol, pitting occurs in only a few seconds so quantitive comparison for minute differences in concentration of additive are difficult to quantify. This is particularly true since the onset of pitting is somewhat subjective.